MgO-based coating for electrically insulating semiconductive substrates and production method thereof

Abstract

The present invention relates to a magnesium oxide-based (MgO) inorganic coating intended to electrically insulate semiconductive substrates such as silicon carbide (SiC), and to a method for producing such an insulating coating. The method of the invention comprises the steps of preparing a treatment solution of at least one hydrolysable organomagnesium compound and/or of at least one hydrolysable magnesium salt, capable of forming a homogeneous polymer layer of magnesium oxyhydroxide by hydrolysis/condensation reaction with water; depositing the treatment solution of the hydrolysable organomagnesium compound or of the hydrolysable magnesium salt, onto a surface to form a magnesium oxide-based layer; and densifying the layer formed at a temperature of less than or equal to 1000° C.

The invention claimed is: 
     
       1. Method for producing a magnesium oxide-based electronically insulating inorganic layer, said method comprising the following steps:
 (a) preparing a treatment solution of at least one hydrolysable organomagnesium compound, capable of forming a homogeneous polymer layer of magnesium oxyhydroxide by hydrolysis/condensation reaction with water; 
 (b) depositing the treatment solution of the hydrolysable organomagnesium compound onto a surface in order to form a magnesium oxide-based layer; and 
 (c) densifying the layer formed at a temperature of less than or equal to 1000° C. in order to obtain the magnesium oxide-based insulating layer, 
 wherein said treatment solution optionally further comprises
 (i) one or more magnesium salts of formula (II):
   MgA 2   (II)
 
 
 
 in which A is a halide ion; and/or
 (ii) one or more metal or metalloid salts or organometallic compounds of general chemical formula (III):
   E t M u   (III)
 
 
 
 in which:
 M is a metal or a metalloid; 
 E is a group chosen from:
 a hydrolysable group; 
 a complexing agent; 
 a β-diketone or a derivative of β-diketone; 
 a phosphonate; 
 a hydroxamate of formula R 16 —CO(NHOH), in which R 16  is a linear or branched alkyl group having from 1 to 30 carbon atoms or a phenyl group; 
 an organosilane; 
 a sulphonate; 
 a borate; or 
 a diol of formula HO—R 16 —OH, in which R 16  is a linear or branched alkyl group having from 1 to 30 carbon atoms, or a phenyl group, wherein t and u, 
 
 respectively, represent the stoichiometry of E and M such that the compound (III) is an electrically neutral compound; 
 
 in a solvent, 
 wherein the solvent of the treatment solution is an organic solvent selected from the group consisting of a saturated or unsaturated aliphatic alcohol of formula R 5 —OH, in which R 5  represents an alkyl group having from 1 to 30 carbon atoms, or a phenyl group; and a diol of formula HO—R 6 —OH, in which R 6  represents an alkyl group having from 1 to 30 carbon atoms, or a phenyl group. 
 
     
     
       2. Method according to  claim 1 , in which the surface is made from a semiconductor or conductor material. 
     
     
       3. Method according to  claim 1 , in which the surface is made from silicon, silicon carbide, gallium arsenide, indium phosphide, gallium nitride, diamond, germanium, or combinations of these materials. 
     
     
       4. Method according to  claim 1 , in which the surface is made from silicon carbide. 
     
     
       5. Method according to  claim 1 , in which the surface is a metal surface. 
     
     
       6. Method according to  claim 1 , in which the surface is made from steels, aluminum, zinc, nickel, iron, cobalt, copper, titanium, platinum, silver, gold, or an alloy of these metals; or an alloy comprising brass, bronze, aluminum or tin. 
     
     
       7. Method according to  claim 1 , in which the surface is a mixed surface. 
     
     
       8. Method according to  claim 1 , in which the treatment solution is obtained by dissolving a molecular compound of magnesium with the general chemical formula (I):
   X y X′ z Mg  (I)
 
 
       wherein X and X′ are chosen independently from:
 a hydrolysable group of formula O—R 1 , in which R 1  is a linear or branched alkyl group having from 1 to 10 carbon atoms; 
 a complexing agent of formula R 2 —COOH, in which R 2  is a linear or branched alkyl group having from 1 to 30 carbon atoms, or a phenyl group; or 
 a β-diketone or a derivative of a β-diketone of formula R 3 —COCH 2 CO—R 4 , in which R 3  and R 4  are chosen independently from a linear or branched alkyl group having from 1 to 30 carbon atoms, or a phenyl group; 
 
       wherein y and z represent respectively the stoichiometry of X and X′ and are such that the first molecular compound is an electrically neutral compound. 
     
     
       9. Method according to  claim 8 , in which O—R 1  is chosen from a methylate, an ethanolate or a propylate. 
     
     
       10. Method according to  claim 1 , in which the solvent comprises methanol, ethanol, isopropanol, butanol or pentanol. 
     
     
       11. Method according to  claim 1 , in which the hydrolysable organomagnesium compound is Mg(OCH 3 ) 2 , Mg(OCH 2 CH 3 ) 2  or Mg(OCH 2 CH 2 CH 3 ) 2 . 
     
     
       12. Method according to  claim 10 , in which the treatment solution is prepared with methanol or ethanol. 
     
     
       13. Method according to  claim 1 , in which the magnesium salt is MgCl 2  or MgBr 2 . 
     
     
       14. Method according to  claim 1 , in which the deposition of the treatment solution is carried out by a liquid processing technique chosen from the group consisting of dip coating, spin coating, sputtering, laminar-flow coating, spray coating, slip coating and techniques using a horizontal blade. 
     
     
       15. Method according to  claim 1 , in which the densification is carried out by a means chosen from the group consisting of a UV radiation, a heat treatment, a UV exposure treatment, a laser-beam irradiation treatment, an electron or ion beam treatment and a microwave energy treatment. 
     
     
       16. Method according to  claim 1 , in which the densification is carried out in an oven or via infrared exposure at a temperature of 400 to 1000° C. 
     
     
       17. Method according to  claim 16 , in which the treatment is carried out for a duration of 2 to 150 minutes. 
     
     
       18. An electronically insulating semiconductor/metal interface of an electronic or optoelectronic component produced by the method according to  claim 1 . 
     
     
       19. An electronically insulating inter-component interface of an electronic or optoelectronic component produced by the method according to  claim 1 . 
     
     
       20. Method of manufacturing an electronic component comprising
 producing a magnesium oxide-based electronically insulating inorganic layer for an electronic component according to the method of  claim 1 , 
 wherein the electronic component is chosen from the group consisting of power diodes, thyristors, transistors and non-volatile RAM memories. 
 
     
     
       21. Method of manufacturing an optoelectronic component comprising
 producing a magnesium oxide-based electronically insulating inorganic layer for an optoelectronic component according to the method of  claim 1 , 
 wherein the optoelectronic component chosen from the group consisting of switches and detectors. 
 
     
     
       22. Method for coating a surface of a conductive or semiconductive substrate with a magnesium oxide-based electronically insulating inorganic layer, said method comprising the following steps:
 (a) preparing a treatment solution of at least one hydrolysable organomagnesium compound capable of forming a homogeneous polymer layer of magnesium oxyhydroxide by hydrolysis/condensation reaction with water; 
 (aa) optionally, preparing the surface of the substrate to be coated in order to improve the adhesion and/or the electrical insulation and/or the abrasion resistance properties of the magnesium oxide-based insulating layer; 
 (b′) depositing the treatment solution of the hydrolysable organomagnesium compound onto the surface of the substrate, optionally prepared via step (aa), in order to form a magnesium oxide-based layer; and 
 (c) densifying said layer formed at a temperature of less than or equal to 1000° C. in order to obtain the magnesium oxide-based insulating layer, 
 wherein said treatment solution further comprises
 (i) one or more magnesium salts of formula (II):
   MgA 2   (II)
 
 
 
 in which A is a halide ion; and/or
 (ii) one or more metal or metalloid salts or organometallic compounds of general chemical formula (III):
   E t M u   (III)
 
 
 
 in which:
 M is a metal or a metalloid; 
 E is a group chosen from:
 a hydrolysable group; 
 a complexing agent; 
 a β-diketone or a derivative of β-diketone; 
 a phosphonate; 
 a hydroxamate of formula R 16 —CO(NHOH), in which R 16  is a linear or branched alkyl group having from 1 to 30 carbon atoms or a phenyl group; 
 an organosilane; 
 a sulphonate; 
 a borate; or 
 a diol of formula HO—R 16 —OH, in which R 16  is a linear or branched alkyl group having from 1 to 30 carbon atoms, or a phenyl group, wherein t and u, respectively, represent the stoichiometry of E and M such that the compound (III) is an electrically neutral compound; 
 
 
 in a solvent, 
 wherein the solvent of the treatment solution is an organic solvent selected from the group consisting of a saturated or unsaturated aliphatic alcohol of formula R 5 —OH, in which R 5  represents an alkyl group having from 1 to 30 carbon atoms, or a phenyl group; and a diol of formula HO—R 6 —OH, in which R 6  represents an alkyl group having from 1 to 30 carbon atoms, or a phenyl group. 
 
     
     
       23. Method according to  claim 22 , in which the surface is made from a semiconductor or conductor material. 
     
     
       24. Method according to  claim 22 , in which the surface is made from silicon, silicon carbide, gallium arsenide, indium phosphide, gallium nitride, diamond, germanium, or combinations of these materials. 
     
     
       25. Method according to  claim 22 , in which the surface of the substrate is made from silicon carbide. 
     
     
       26. Method according to  claim 22 , in which the surface is a metal surface. 
     
     
       27. Method according to  claim 22 , in which the surface is made from steels, aluminum, zinc, nickel, iron, cobalt, copper, titanium, platinum, silver, gold, or an alloy of these metals; or an alloy comprising brass, bronze, aluminum or tin. 
     
     
       28. Method according to  claim 22 , in which the surface is a mixed surface. 
     
     
       29. Method according to  claim 22 , in which the treatment solution is obtained by dissolving, in a solvent, a first molecular compound of magnesium with the general chemical formula (I):
   X y X′ z Mg  (I)
 
 
       wherein X and X′ are chosen independently from:
 a hydrolysable group of formula O—R 1 , in which R 1  is a linear or branched alkyl group having from 1 to 10 carbon atoms; 
 a complexing agent of formula R 2 —COOH, in which R 2  is a linear or branched alkyl group having from 1 to 30 carbon atoms, or a phenyl group; or 
 a β-diketone or a derivative of a β-diketone of formula R 3 —COCH 2 CO—R 4 , in which R 3  and R 4  are chosen independently from a linear or branched alkyl group having from 1 to 30 carbon atoms, or a phenyl group; 
 
       wherein y and z represent respectively the stoichiometry of X and X′ and are such that the first molecular compound is an electrically neutral compound. 
     
     
       30. Method according to  claim 29 , in which O—R 1  is chosen from a methylate, an ethanolate or a propylate. 
     
     
       31. Method according to  claim 29 , in which the solvent comprises methanol, ethanol, isopropanol, butanol or pentanol. 
     
     
       32. Method according to  claim 22 , in which the hydrolysable organomagnesium compound is Mg(OCH 3 ) 2 , Mg(OCH 2 CH 3 ) 2  or Mg(OCH 2 CH 2 CH 3 ) 2 . 
     
     
       33. Method according to  claim 31 , in which the treatment solution is prepared with methanol or ethanol. 
     
     
       34. Method according to  claim 22 , in which the magnesium salt is MgCl 2  or MgBr 2 . 
     
     
       35. Method according to  claim 22 , in which the deposition of the treatment solution is carried out by a liquid processing technique chosen from the group consisting of dip coating, spin coating, sputtering, laminar-flow coating, spray coating, slip coating and techniques using a horizontal blade. 
     
     
       36. Method according to  claim 22 , in which the densification is carried out by a means chosen from the group consisting of a UV radiation, a heat treatment, a UV exposure treatment, a laser-beam irradiation treatment, an electron or ion beam treatment and a microwave energy treatment. 
     
     
       37. Method according to  claim 22 , in which the densification is carried out in an oven or via infrared exposure at a temperature of 400 to 1000° C. 
     
     
       38. Method according to  claim 37 , in which the treatment is carried out for a duration of 2 to 150 minutes. 
     
     
       39. An electronically insulating semiconductor/metal interface of an electronic or optoelectronic component produced by the method according to  claim 22 . 
     
     
       40. An electronically insulating inter-component interface of an electronic or optoelectronic component produced by the method according to  claim 22 . 
     
     
       41. Method of manufacturing an electronic component comprising
 producing a magnesium oxide-based electronically insulating inorganic layer for an electronic component according to the method of  claim 22 , 
 wherein the electronic component is chosen from the group consisting of power diodes, thyristors, transistors and non-volatile RAM memories. 
 
     
     
       42. Method of manufacturing an optoelectronic component comprising
 producing a magnesium oxide-based electronically insulating inorganic layer for an optoelectronic component according to the method of  claim 22 , 
 wherein the optoelectronic component chosen from the group consisting of switches and detectors. 
 
     
     
       43. Electronically insulating inorganic layer obtained by the method of  claim 1 . 
     
     
       44. Method for coating a surface of a conductive or semiconductive substrate with a magnesium oxide-based electronically insulating inorganic layer, said method comprising the following steps:
 (a) preparing a treatment solution of at least one hydrolysable organomagnesium compound capable of forming a homogeneous polymer layer of magnesium oxyhydroxide by hydrolysis/condensation reaction with water; 
 (aa) preparing the surface of the substrate to be coated in order to improve the adhesion and/or the electrical insulation and/or the abrasion resistance properties of the magnesium oxide-based insulating layer; 
 (b′) depositing the treatment solution of the hydrolysable organomagnesium compound onto the surface of the substrate, prepared via step (aa), in order to form a magnesium oxide-based layer; and 
 (c) densifying said layer formed at a temperature of less than or equal to 1000° C. in order to obtain the magnesium oxide-based insulating layer, 
 wherein said treatment solution further comprises
 (i) one or more magnesium salts of formula (II):
   MgA 2   (II)
 
 
 
 in which A is a halide ion; and/or
 (ii) one or more metal or metalloid salts or organometallic compounds of general chemical formula (III):
   E t M u   (III)
 
 
 
 in which:
 M is a metal or a metalloid; 
 E is a group chosen from:
 a hydrolysable group; 
 a complexing agent; 
 a β-diketone or a derivative of β-diketone; 
 a phosphonate; 
 a hydroxamate of formula R 16 —CO(NHOH), in which R 16  is a linear or branched alkyl group having from 1 to 30 carbon atoms or a phenyl group; 
 an organosilane; 
 a sulphonate; 
 a borate; or 
 a diol of formula HO—R 16 —OH, in which R 16  is a linear or branched alkyl group having from 1 to 30 carbon atoms, or a phenyl group, wherein t and u, respectively, represent the stoichiometry of E and M such that the compound (III) is an electrically neutral compound; 
 
 
 in a solvent, 
 wherein the solvent of the treatment solution is an organic solvent selected from the group consisting of a saturated or unsaturated aliphatic alcohol of formula R 5 —OH, in which R 5  represents an alkyl group having from 1 to 30 carbon atoms, or a phenyl group; and a diol of formula HO—R 6 —OH, in which R 6  represents an alkyl group having from 1 to 30 carbon atoms, or a phenyl group.